The present invention relates to an ink composition, more particularly, to a water-soluble magenta ink composition for ink-jet recording comprising a anthrapyridone compound or the salt thereof that has a wide color range and is excellent in color tone, light fastness and water fastness; and a method of ink-jet recording thereby.
Diverse ink jetting processes have been developed for the recording method by means of ink-jet printer, and any processes comprise generating ink droplets to deposit onto various recording materials (such as paper, film, cloth) for recording. The recording method by means of ink-jet printer has rapidly been spread in recent years and will be propagated in future because the method brings about no noise due to the system in which a recording head does not contact with the recording material and because the method advantageously allows the printer to become downsized, to work in a high-speed and to give color printing, easily. In order to record in color an image information or a character information on a computer color display by an ink-jet printer, the information is generally printed by subtractive color mixing of inks of four colors, namely yellow(Y), magenta(M), cyan(C) and black(K). In order to print reproducibly an image pictured by additive color mixing of R(red), G(green), B(blue) on a CRT display as identical as possible by subtractive color mixing, the dyes used therefor, especially the ones for a YMC ink, are desired to have color hues close to the respective standards of YMC(xe2x80x9cJapan Color Standard Paperxe2x80x9d published by Japan Printing Machinery Manufacturers Association)and vividness. Additionally, it is required that the resulting ink composition is stable for long-term storage and that the resulting printed image is of a high optical density and has excellent fastness including water fastness, light fastness, and outdoor exposure fastness. Outdoor exposure fastness is a complex fastness to light and atmospheric gas such as the oxide gas of nitrogen or sulfur and ozone.
The present invention relates to a magenta ink.
The uses of ink-jet printers are enlarged from a small one for office use to a big one for industry. So, excellence in fastness such as water fastness and light fastness of the printed image is more keenly demanded. The water fastness of an article recorded by ink-jet printing has been improved substantially by coating inorganic or organic micro particles such as cationic polymer, porous silica, alumina sol and special ceramics which can absorb dye from ink, on a paper sheet together with the resins such as PVA resin. Various coated sheets for ink-jet printing are already available on the market. But light fastness has not yet been largely improved by any established technique. Magenta, one of tetrachromatic colors of YMCK, of which dyes are originally poor in light fastness, and the improvement is an important problem to be solved. Further, the articles recorded by magenta dyes have been found to fade in color while being exposed to light and air, possibly because of the influences of the various gasses existing in nature.
The chemical structure of magenta dyes used in a water-soluble ink for ink-jet recording are a xanthene type disclosed by JP Laid-Open No.89811/1979, JP Laid-Open No.60053/1996 and JP Laid-Open No.143798/1996, and an azo type using the H acid disclosed by JP Laid-Open No.62562/1986, JP Laid-Open No.156168/1987, JP Laid-Open No.203970/1991, JP Laid-Open No.157698/1995 and JP Publication No.78190/1995. The xanthene type is indeed excellent in hue and vividness, but is very inferior in light fastness. Some of the azo type using the H acid are good in hue and water fastness, but are inferior in light fastness and vividness. As disclosed by JP Laid-Open No.203970/1991, magenta dyes having excellent vividness and light fastness have been developed in this type, but are still inferior in light fastness to the dyes of other colors such as azo yellow dyes and cyan dyes represented by copper phthalocyanine type.
Furthermore, for a chemical structure of magenta dyes having excellent vividness and light fastness, an anthrapyridone type is known as disclosed by JP Laid-Open No.195775/1982, JP Laid-Open No.74173/1984 and JP Laid-Open No.16171/1990 but is not yet able to satisfy all of the properties such as the range of color, hue, vividness, light fastness, water fastness and stability in solution. An anthrapyridone compound is described as a dye having good light fastness and water fastness in U.S. Pat. No. 2,644,821. However, it is a dye mainly for fiber dyeing and can not provide a high quality ink suitable for ink-jet recording.
An object of the present invention is to provide a water-based magenta ink composition which has hue of a wide color range and vividness suitable for ink-jet recording and gives the recorded material with a high fastness and a magenta dye suitable therefor.
The present inventors made a diligent study to solve the above problem and, as a result, have completed the present invention. Namely, the present invention is as follows:
(1) An anthrapyridone disulfonic acid represented by Formula (1) or the salt thereof 
(2) A dye mixture being obtained by sulfonating the anthrapyridone compound represented by Formula (2), comprising the disulfonic acid product of the anthrapyridone compound represented by Formula (2) or the salt thereof and the monosulfonic acid product of the anthrapyridone compound represented by Formula (2) or the salt thereof. 
(3) A dye mixture according to the above (2), wherein said disulfonic acid product of the anthrapyridone compound represented by Formula (2) or the salt thereof has a content of 85% or more and said monosulfonic acid product of the anthrapyridone compound represented by Formula (2) or the salt thereof has a content of 10% or less, when determined from their area ratios by high performance liquid chromatography (HPLC).
(4) A dye mixture according to the above (3), wherein said disulfonic acid product of the anthrapyridone compound represented by Formula (2) or the salt thereof has a content of 90% or more and said monosulfonic acid product of the anthrapyridone compound represented by Formula (2) or the salt thereof has a content of 5% or less, when determined from their area ratios by high performance liquid chromatography (HPLC).
(5) A dye mixture according to any one of the above (2) to (4) comprising an inorganic salt having a content of 1% by mass or less.
(6) A dye mixture according to any one of the above (2) to (5), wherein one of said disulfonic acid product of the anthrapyridone compound represented by Formula (2) is the anthrapyridone disulfonic acid represented by Formula (1).
(7) A method for producing the anthrapyridone disulfonic acid or the salt thereof according to the above (1), characterized in that the anthrapyridone compound represented by Formula (2) is disulfonated with fuming sulfuric acid, followed by salting out the obtained reaction solution by a conventional way to get a wet cake, which is then treated with hydrous lower alcohol.
(8) A method for producing the dye mixture according to any one of the above (2) to (6), characterized in that the anthrapyridone compound represented by Formula (2) is sulfonated with fuming sulfuric acid, followed by salting out the obtained reaction solution comprising the disulfonic acid product and the monosulfonic acid product of the anthrapyridone compound represented by Formula (2) by a conventional way.
(9) A water-based magenta ink composition that contains the anthrapyridone disulfonic acid according to the above (1) or the salt thereof.
(10) A water-based magenta ink composition that contains the dye mixture according to any one of the above (2) to (6).
(11) A water-based magenta ink composition according to the above (9) or (10), wherein said composition contains water and an organic solvent.
(12) A water-based magenta ink composition according to any one of the above (9) to (11), wherein said composition is prepared for ink-jet recording.
(13) A method for ink-jet recording that ink droplets are ejected responding to record signals to record onto a recording material, comprising using the water-based magenta ink composition according to any one of the above (9) to (12) as a magenta ink.
(14) A method for ink-jet recording that ink droplets are ejected responding to record signals to record onto a recording material, comprising using the water-based magenta ink composition according to any one of the above (9) to (12) as a magenta ink and using a water-based cyan ink composition containing a water-soluble metal phthalocyanine dye as a cyan ink.
(15) A method for ink-jet recording according to the above (13) or (14), wherein said recording material is a fiber material having polyamide groups and the fiber material is treated by heat after said ink droplets are ejected on it.
(16) A method for ink-jet recording according to any one of the above (13) to (15), wherein said recording material is an information transmission sheet.
(17) A method for ink-jet recording according to the above (16), wherein said information transmission sheet is a surface-finished sheet.
(18) An ink-jet printer that comprises being equipped with a container containing the water-based magenta ink composition according to any one of the above (9) to (12) and further a container containing a water-based cyan ink composition containing a water-soluble metal phthalocyanine dye.